Hormone replacement therapy (HRT) in postmenopausal women is the focus of considerable research interest because its benefits may include reductions in risk for coronary heart disease and osteoporosis, as well as protection against declines in cognitive functioning, particularly memory performance. We propose to obtain preliminary data to test the hypothesis that one of the basic mechanisms responsible for the beneficial memory effects of HRT is an attenuation of hypothalamic-pituitary-adrenal (HPA) axis reactivity. The study will test for HRT-associated attenuation of cortisol reactivity to challenge and protection against memory impairment by comparing three groups of women: 30 taking an estrogen/progestin regimen [EP], 30 taking estrogen-only [E-only], and 30 not using HRT [no-HRT]. The women will participate in a standardized social-cognitive challenge (having to give a talk to a panel of evaluators), administered at the UCLA Clinical Research Center; patterns of salivary "free" cortisol reactivity to the challenge will be assessed to test the hypothesis that HRT is associated with attenuated HPA axis reactivity. Memory performance will be assessed pre and post-challenge to test the hypothesis that women using HRT will show smaller declines as a consequence of their smaller cortisol elevations during the challenge. Results from this study will be used as preliminary data for an R0I application for an HRT clinical trial designed to further elucidate the basic mechanisms of HRT effects on the HPA axis, including ACTH and CRH regulation, and to demonstrate, in an experimental design, HRT effects on cortisol regulation and the impact of this on memory performance.